Note: Descriptions are shown in the official language in which they were submitted.
~06~932
TEMPERArrURE DETECTOR
Back round of the Invention
g
Temperature detectors which employ thermistors
in operating contact with an environment which is being
monitored for temperature has many uses, more particularly
in our modern society which is becoming more energy conscious.
I Protection of the thermistor ~rom that environment, while
simultaneously permitting heat transfer on a uniform basis
to permit accurate monitoring, is a major concern. This is
true particularly when the environment and/or the temperature
range is extreme.
When a thermistor is directly soldered onto the
inner bottom of a protection tube, the thermistor will be
reliably connected to the tube. This, however, is a diffi-
cult operation because the silver electrode surface of the
thermistor easily reacts with the solder. Moreover,
protection tubes are normally formed by cutting and
machining metal, which results in a surface which is
not completely smooth and uniform. Oxidation can then
develop during the use of the device over varying tempera-
ture cycles, giving rise to the occurrence of contact
resistance.
-~ Accoraingly, it is an object of this invention
to provide a method for utilizing a thermistor in a
' 25 protection tube as a sensing device for temperature.
Another object of this invention is to provide
a device which is capable of withstanding acyclic tempera-
~ ~ ture changes without damage to the heat trans~er appaxatus
'r.' from the pro-tection tube to the thermistor.
Other objects will appear hexeinafter.
:
' ~
.'r~
_, . _ .. _ _.. _ _ _ . . _ . -- . --.
- ~6~3Z
Brief Description of the Invention
Accordingly, it has been discovered that a tempera-
ture device according to the principles of this invention
may be provided to accomplish the above and other objects of
this invention. Specifically, a protection tube means is
provided having a ~lat inner bottom surface and a top open-
ing end. A resilient metallic member is positioned within
the tube means, with the member having a bottom portion
essentially parallel to the bottom surface~of the tube and
in substantial surface contact therewith. The member has
a remaining portion which is essentially perpendicular
to the bottom portion, slightly longer than the distance
between the bottom surface and the top opening of the tube
means. A thin layer of metal, softer than the member, is
positioned between the bottom portion of the member and the
bottom surace to increase contact. A thermistor means is
mounted on the remaining portion of the member. Finally,
tube closing means are provided to fit on the top of the tube
.
means and positioned to compress the remaining portion of
the member to thereby urge contact between the bottom por-
tion of the member and the bottom surface of the tube.
In accordance with this invention there is provided
' a temperature detecting device comprising: a protective
tube means having a flat inner bottom surface and a top open-
`` 25 ing end; a resilient metallic member positioned within said
' tube means, said member havin~ a bottom portion essentially
parallel to said bottom surface and in substantial surface
contact therewith, said member having the remaining portion
essentially perpendicular to said bottom portion and slightly
~` 30 longer than the distance between the bottom surface and the
` top opening end of said tube; a thin layer of metal, softer
than said member, positioned between said portion of said mem-
- - . , ,. - .:''. '. ' .' - :~'
:, : , . ,. ~:
-
-` ~Q68~32
ber and said bottom surface; a thermistor means mounted
on said remaining portion of said memberi and a tube closing
means adapted to fit on said top opening end of said tube
means, positioned to compress the remaining portion of
said member to thereby urge contact between said bottom
portion o~ said member and bottom surface of said tube means.
In a preferred embodiment, the bottom portion of
the member is split to position the remaining portion of the :
member relatively centrally in the tube means. Also pre-
ferred is to provide the remaining portion of said member
with a bifurcated section adapted to permit each bifurcated
part to bend in opposite direc~ion to the other upon com-
pression of the member by said closing means. This compression
of the bifurcated sections not only assists in maintaining
i 15 contact between the bottom portion of the-member and the -~
; ~ bottom surface of the tube but further assists in center-
ing the member within the tube.
In a urthex preferred embodiment, the thin layer
o metal, softer than said member, which is positioned
between the bottom portion of the member and the bottom
surface of the tube, should be selected from the group con-
~-- sisting of gold, silver, nickel, and solder.
Detailed Description of the Invention
~ For a more complete understanding of the invention,
reference is hereby made to the drawings in which:
, FIGURE 1 represents a partially cutaway view of
the preferred embodiment of the present invention; and
FIGURE 2 is a view of a novel element used in the
embodiment of FIGURE 1.
With reference to FIGURE 1, the metal place 10
which forms a resilient metallic member of this invention
6893'~
and to which is joined the thermistor 2 is studded in a
notch of an insulation place 3 and inserted into the
protection tube 1. A pair of terminals 4 and 5 are studded
on the insulation place 3, one terminal 4 being connected
to the thermistor 2 and the other terminal 5 being connected
to the prot~ction tube 1 through a conducto~ 6. When an
opening port of the protection tube 1 is closed with the
insulation plate 3 via a packing 7, the metallic plate
or member 10 is urged into contact between the bottom
portion of the member and the bottom surface of the tube.
As shown in FIGURE 2, the metallic resilient
member 10 is formed from a piece of resilient metal plate
by means of a punch press, a casting, or such. In the
central part of the place 10, a plate is divided into
two paths defining a bifurcated section to form pieces
: 11 and 12. The bottom portion of the member 10 is formed
by olding pieces 13 and 14 into opposite directions such
., that they are perpendicular to the remaining portion of the
member 10. When the packing 7 is closed with the insula-
tion plate 3, the resilient nature of the metallic member
~ forces pieces 13 and 14 into close contact with the bottom
- ; of the tube 1. The bifurcated portions 11 and 12 of the
member 10 are curbed in the shape of bows in the opposite
` direction to one another, thereby providing a uniform and
permanent pressure while simultaneously permitting center-
.~
:' ing of the force against the bottom portions 13 and 14. The
-~ thermistor itself is mounted in the member 10 at the area
shown by dotted line 15.
In ordex to obtain maximum contact between the
metal place 10 and the inner bottom surface of the tube 1,
.: .: : . .
1~6~93Z
an electroplating 8 of a metal softer than the metal plate 10
is employed, either on the inner bottom surface of the tube
or on the surface pieces 13 and 14 of the metal plate 10
contacting the bottom of the tube. Metals such as gold,
silver, nickel, solder and other metals which are softer
than the metal plate 10 may be employed. The metal plate
10 is made of a resilient material such as, for example,
the metals used for blades of switches, and does not have
the ability to provide sufficient contact between its inner
bottom surface of protection tube 1. Therefore, an electro-
plating of a soft metal, and particularly one which does
not oxidize, permits the contacting pressure from the
bifurcated portions of 11 and 12 of the member to force
the areas 13 and 14 into contact with the electroplating
8 to ensure uniform and permanent contact with the bottom
of the tube 1.
Temperature detectors built under the principles
of this invention have been manufactured and employed in
: ~ .
tests over substantial temperature variations. Since the
effective contacting area remains constant, no variation
in operating characteristics were detected and the device
was found to be satisfactory and essentially trouble
free.
, ., . .. . . .. . . .. .. ... ~ .. . . . . .. .. .... .
